class base {
    int age;
    String name;
    public base(int age, String name) {
        this.age = age;
        this.name = name;
    }
}
class Derived extends base{
    int sum;
    public Derived(int age, String name) {
// super(); // 注意子类构造方法中默认会调用基类的无参构造方法：super(),
// 用户没有写时,编译器会自动添加，而且super()必须是子类构造方法中第一条语句，
// 并且只能出现一次
        super(age, name);
        this.sum = 0;
    }
}
public class ABC {
    public static void main(String[] args) {
        Derived d = new Derived();
    }
}